Re: [PATCH v4 7/8] mtd: rawnand: arasan: Add new Arasan NAND controller

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Boris,

Boris Brezillon <boris.brezillon@collabora.com> wrote on Sun, 10 May
2020 09:02:30 +0200:

> On Fri,  8 May 2020 19:13:38 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > +static int anfc_len_to_steps(struct nand_chip *chip, unsigned int len)
> > +{
> > +	unsigned int steps = 1, pktsize = len;
> > +
> > +	while (pktsize > ANFC_MAX_PKT_SIZE) {
> > +		steps *= 2;
> > +		pktsize = DIV_ROUND_UP(len, steps);
> > +	}  
> 
> 
> Same here, you shouldn't have a round_up() but instead complain if
> "len != pkt_size * steps"
> 
> 	if (len % 4)
> 		return -ENOTSUPP;
> 
> 	if (len < ANFC_MAX_PKT_SIZE)
> 		return len;
> 
> 	for (steps = 2; steps < ANFC_MAX_STEPS; steps *= 2) {
> 		pkt_size = len / steps;
> 		if (pkt_size <= ANFC_MAX_PKT_SIZE)
> 			break;
> 	}
> 
> 	if (pkt_size * steps != len)
> 		return -ENOTSUPP;
> 
> 	return pkt_size;
> 
> > +
> > +	if (steps > ANFC_MAX_STEPS)
> > +		return -ENOTSUPP;
> > +
> > +	return steps;
> > +}  

I took the logic of the above proposal and extended the helper to be
"anfc_pkt_len_config", taking two pointers as argument: *steps and
*pktsize, which will be updated in case of success. Otherwise
this function returns an error and can be added to the "check_op" path
instead of only failing at execution time.

---8<---

+static int anfc_pkt_len_config(unsigned int len, unsigned int *steps,
+                              unsigned int *pktsize)
+{
+       unsigned int nb, sz;
+
+       for (nb = 1; nb < ANFC_MAX_STEPS; nb *= 2) {
+               sz = len / nb;
+               if (sz <= ANFC_MAX_PKT_SIZE)
+                       break;
+       }
+
+       if (sz * nb != len)
+               return -ENOTSUPP;
+
+       if (steps)
+               *steps = nb;
+
+       if (pktsize)
+               *pktsize = sz;
+
+       return 0;
+}

--->8---

And then, in anfc_check_op():

+               case NAND_OP_DATA_IN_INSTR:
+               case NAND_OP_DATA_OUT_INSTR:
+                       if (instr->ctx.data.len > ANFC_MAX_CHUNK_SIZE)
+                               return -ENOTSUPP;
+
+                       if (anfc_pkt_len_config(instr->ctx.data.len NULL, NULL))
+                               return -ENOTSUPP;
+
+                       break;

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